Mid-Autumn Festival happens every year on the 15th day of the 8th month according to the Lunar calendar. The popular harvest festivities are celebrated by the Chinese, Vietnamese, Japanese and Koreans. There are so many variations of the story behind this day.
My favorite one is the story about how the Chinese used their cleverness to defeat the Mongol empire. In ancient times, people told time based on their surroundings. The Chinese were able to synchronized their tactics by picking a day when the moon was the biggest and brightest - the 15th day of the 8th month. Because the Mongols did not fancy mooncakes, the Chinese were able to spread the message about a coordinate attack by sending mooncakes with hidden messages inside. They successfully the Mongol empire and established the Ming dynasty.
Check out the photos below for photos of the Mid-Autumn festivals.